 In some lasers the gain is very low, so the beam must make hundreds of passes through the medium for sufficient gain.In this case the output coupler may be as high as 99% reflective, transmitting only 1% of the cavity's beam to be used.A dye laser has very high gain compared to most solid-state lasers, so the beam needs to make just a few passes through the liquid to reach its optimum gain, thus the output coupler is typically around 80% reflective.